Automatic braking apparatus for aircraft



Oct. 20, 1953 H. w. TREvAsKls AUTOMATIC BRAKING APPARATUS FOR AIRCRAFT 4Sheets-Sheet l Filed Nov. 14, 1950 A@ @WWA 4 @7% Oct'. 20, 1953 H. w.TREVASKIS 2,656,017

AUTOMATIC BRAKING APPARATUS FOR AIRCRAFT Filed Nov. 14, 1950 4Sheets-Sheet 2 Oct. 20, 1953 H. w. TREvAsKlsV 2,656,017

AUTOMATIC BRAKING APPARATUS FOR AIRCRAFT Filed Nov. 14, 1950 4Sheets-Sheet 5 muy Oct. 20, 1953 H. w. TREVAsKls 2,656,017

AUTOMATIC BRAKING APPARATUS FOR AIRCRAFT Filed Nov. 14, 1950 4Sheets-Sheet 4 Patented Oct. 20, 1953 AUTOMATIC BRAKING APPARATUS FORAIRCRAFT Henry William Trevaskis, Solihull, England, as-

s'gnor to Dunlop Rubber Company Limited, London County, England, aBritish company l 14, 1950, Serial No. 195,509 InGreat Britain November17, 1949 Applicationv November 16 Claims. 1

This invention relates Ito an automatic vbraking system for aircraft.

When an aircraft having a Wheeled or a tracked under-carriage lands, thebrakes are normally applied by the pilot shortly 'after the iirst impactof landing. The brakes, which maybe either hydraulicallyorlpneumaticallyoperated,-are usually applied throu'gha valve under thecontrol of .the pilot, the braking pressure on the -whcel brakes beingicommensurate with, Je. g., `the Iangular movement of 'the valve lever.A great deal of earemustb'e `exercised by the pilot when braking, since`ith'e brakes A.are appliedtoo hard'the wheels will lock, "withy-consecment v:damage to the tires, andlil noti-applied hard enoughthe'aircrait may overrun the landing strip. There is .always :a definite-pressure 'that should 'not be exceeded wlhen it is required t'o lbrakethe aircraft .without damage to the tires, .and this pressure :may beden'ed as fthe vmaximum pressure which may be applied to the brakewithout causing the wheel to d'ecelerate'so violently as'to causeskiddingfof the tyre on the landing surface. This pressure is 'notconstant, but lis dependant upon a number of factors, amongst .themybeing the ground speed of the aircraft, the total weight -of theaircraft carried by the wheelsand the .nature ofthe landing surface.

When 'land-ing, the .pilot of the .aircraft vrhas many other duties toattend to, apart .from selectively .controlling the braking pressure atvarious stages along the landing run. It is thereforedesirable tovprovide .an automatic braking apparatus which will,to alarge extent,relieve the pilot of any duties in connection with .the brakes .otherthan that .of Vthe `initial application. Such an apparatus .should `be.capable of automatically controlling the lbraking lpressures .duringthe landing run. A'l'.t`is the object of this invention to provide anautomatic brake apparatus of this nature.

According to theinvention apparatus "for automatically controlling thebraking pressure in an aircraftflu'id pressure operated wheel brakecompr-ises .a`housing rotatable by a Wheelfa 'flywheel rotatable insaidhOuSing, a drum-.member also rotatable vin said housing and capableof ylimited angular displacement relative Vto said llywhee'l, meansmoveable axially bysa'idangular displacement, "anda `valve mechanism'adapted to be *connectedto asource of 'fluid pressure, to exhaust andto said"brake'and operated l`by 'axial movementor said `mea-ns,lvi'rhereby 'on relative angular displacement between theldrum-memberand finywheel yone vdirection the axially-moveable L2 means operates thevalve mechanism to `reduce the braking pressure and on 'relative angulardisplacement in the other direction lthe axially moveable means operates'the valve mechanism to restore the braking pressure.

Preferably the apparatus comprises a housing rotatable by a wheel, `anannular flywheel rotatable in said housing vhaving a beam extendingdiametrically across the interior thereof, a drummember also rotatable'within lthe 'housing and provided with ltwo diametrically opposed stopsadaptedtocontact the flywheel'beam and restrict angular :movementfof theiiywheelrrelative to the drum-member, a Vclutch mechanism rotatable 'bythe housing land adapted 'to drive 'the ydrummem'ber, -spring means tourge the flywheel into a predetermined angular position relative `to thedrurmmember, means adapted to move axially on angular displacement ofsaid flywheel yrelative to said drum-member :and a valve mecha n-ismoperated -by axial movement of Lsaid lfmeans to Y'control the Asupply of'pressure :fluid 'from `a source to said Wheel brakes, whereby onlrelative angular displacement of 'the `flywheel and 'drum member in onev-directicn the axially-moveable means .operates the valve mechanism toreduce thebrakin'g pressure, and vonrelative angular-displacement of#thevywheel and drum=member 4in the other direction the axially-moveablemeans operates 'the valve Vmecha-nisrn to `restore t'he brakingpressure.

`In the :apparatus of the `present invention the housing Amay beErotated by any vvrotatable `par-t 'of the wheel. 'For example theapparatus may fbe secured to Ione :of the aircraft `wheel struts and thehou'sing may be rotatable by the lside lwall Arof the tireor-by the'edgeof the wheelrirn. Preferabl-y however the apparatus is secured yto 2anon-rotatable part of v'the V'brake apparatus, or example, the torqueAplate, and the housing fis rotatable'bylthe innerperiphery'vdfthevwheelrim, or'byr a 'flange carried `by said rim.

In `order that-the invention lmay vvbe more *fully described, refer-enceis r-made tothe accompanying drawings, of which:

Figure 1 -is a side elevation, `partly iin'section, of an automaticbrake apparatus constructed jin accordance with 'the invention dook-.ing`A:from 'the left Alof V'Figure f2,

Figure 2 is a sectionzt'hrough 'A--A of Figure 1, looking-'in'thefdirection of the arrows. i

"Figure B Vis a par-t' section through lB-LB rofiliigure fl, lookingiin--th'e'direction `of thief-arrows.

Figure 4 is a view from the left of Figuret'Zywith the valve-bodyremoved. Y

Figure is a part section through C-Cv of Figure 2 looking in thedirection of the arrows.

Figure 6 is a part view from the right of Figure 2 with the flywheelcasing and bracket arm removed.

In an embodiment; of the invention (Figures l 'and 2) the apparatuscomprises a flange i adapted to be secured by bolts to a non-rotatableportion of a wheel and brake assembly, for example, the torque plate. Abifurcated bracket integral with the ange has two arms 2 and 3 extendingnormally from the face of the flange. Rotatably mounted in said bracketis a hollow cylindrical housing Il, comprising a radially-extending wallfea and axially-extending peripheral wall 4b integral therewith, and 'aseparable radially-extend wall 4c.

The radial wall 4a of the housing is provided centrally with a boss 5which extends axially an equal distance both interior and exterior ofthe housing, and the periphery of the boss is provided with a metalbearing E. The face of the boss interior of the housing is providedcentrally with a cylindrical recess 1. 'I'he part of the boss exteriorof the housing runs in ball-bearings S which are held between thebearing on said part of the boss and a bearing 9 located in the arm 2 ofthe bifurcatcd bracket adjacent the end of said arm.

The other radial wall 4c of the housing is provided centrally with acircular hole and an annular flange I l, and said flange extends anequal distance both interior and exterior of the housing. The outerperiphery of the flange is provided with metal bearings I, similar tothose on the boss, and the part of the ange exterior of the housing runsin ball-bearings I2 which are held between the bearing on said part ofthe flange and a bearing I3 located in the arm 3 of the bifurcatedbracket adjacent the end of said arm. Sealing rings I4 are provided toprevent ingress of foreign matter to both ball-bearings and I2.

rvhe exterior periphery of the housing, i. e. the axially-extending wall4b, is provided with a solid rubber twin-contact tire I5, which isadapted to Contact the inner periphery of the Wheel rim. :The housingthus rotates freely when the wheel rotates.

An 4annular drum member is fitted within the housing, and saiddrum-member comprises two coaxial drums I3 and I1 spaced apart by twodiametrically opposed substantially arcuate portions IS (Figure 5). Thedrum-member is for convenience made in two parts each comprising halfthe axial width of outer drum I6 and inner drum I1 and a part of thearcuate portions I8, and the two drum parts are held together by screwsI9 and dowels 29 (Fig. 5), passing through the arcuate portions I8. Thetwo ends of the inner periphery of the inner drum I1 seat on thebearings 6 and II on the interior portions of the boss and flangerespectively and may r0- tate on said bearings. The inner drum |1 isprovided with two diametrically opposed, axiallyextending slots 2|, Afora purpose to be later de- 'I'he outer periphery of the outer drum I6 isprovided, in the median plane thereof, with acircumferentially-extending slot 22 (Fig. 2), and on each side of saidslot is a circumferentiallyextending recess 23 of rectangular section.Each of said recesses accommodates a series of ballbearings 25.

An annular space is provided between the outer periphery of the outerdrum I6 and the inner periphery of the housing and an annular flywheel25 of considerable weight is located within said space (Figs. 2 and 5).The inner periphery of the'ywheel is provided with a radially-extendingrib 26 which ts within the slot 22 without contacting the sides or edgesthereof and serves to prevent axial-misalignment of said ball-bearings.The inner periphery of the flywheel rests on said ball bearings whichallow relative rotation between flywheel and drum member with little orno frictional resistance.

The radially-extending face of the flywheel adjacent the housing wall 4ais recessed from a location adjacent its outer periphery to its innerperiphery and said face is provided, adjacent its outer periphery, witha plurality of equispaced, axially-extending blind holes 21 which breakinto the side of said recess. A clock-type coiled spring 28 is tted insaid recess, one end thereof being formed into an eye and secured in oneof said holes 21. The edge of the outer drum I6 adjacent said housingwall la is likewise provided with a plurality of blind holes 29 (Figurev6) which break into the outer periphery of said outer drum, and theinner end of the clocksprng is likewise formed into an eye, which issecured in one of said holes.

A thin beam 3i) of rectangular section extendsA diametrically across theinterior of the flywheel in the median plane thereof, and is integralwith said flywheel. The beam passes between the arcuate portions I8 ofthe drum which act as stops to restrict the relative angular movementbetween the drum and the flywheel. Said beamA is provided with twoequi-sized holes 3| spaced one on each side of the centre of the beamand on the longitudinal axis thereof.

A @am member s2 is siidabiy tted within they inner periphery of theinner drum I1 and said cam member is provided with two diametricallyopposed keys 33 which engage in the slots 2| in fsaid drum. The cammember is thus rotatable with the drum and axially slidable relativethereto. The cam member is fitted between the beam 39 of the flywheeland the boss 5 of the housing, and an anti-friction ball 34 is providedin the recess 1 in the boss against which the plane face of the cammember abuts. The other face of the cam member, i. e. that adjacent thebeam, is provided with a shallow recess of V-section. Two balls 35,situated one in each of said holes 3| of the beam are adapted, in oneangular position of the beam, to lie in the apex of the vv-sectionedrecess in the cam member. The balls are prevented from quitting saidholes by a disc 36 which slidably lits in the inner periphery of theinner drum on the side of the beam remote from the cam member.

A clutch mechanism is fitted in the annular recess between the inner andouter drums I 6 and I1 on that side of the drum member adjacent thehousing .wall 4a. Said clutch comprises two part-annular torque-arms 31and 38 (Figure 6) arranged to form substantially a complete annuluswithin said recess. A clearance is provided between the inner peripheryof each 0f said torque arms 31, 38 and the outer periphery pf the innerdrums I1. A similar clearance is provided between the outer periphery ofeach of said arms 31, 38 and the inner periphery of the outer drum I6except that each of said arms is provided integrally at one end with aradiallyl extending portion 31a, 38a, which frictionally 'engages saidinner periphery. l

The torque Aarm 38,4 adjacent the end remote from the portion 38d, isprovided with an axially extending hole 39 and Fitting in said hole is astud 40 which is secured to the housing wall 4a. Said end is likewiseprovided with a coiled helical springv4l` having oneend secured theretoand the other 'en'ditting a coaxialhole 42 in the 'adjacent end ofthetorgu'e arm 31. i g

The end of torque 'arm 3,1 remote from the portion 31a is providedronits r outer peripheral suriace, withV a rectangular recess, into whichnts a wedge-shaped portion 38o integral with the associated end of thetorque arm 38. The spring 4I thus urges the associated ends oftorque-arms 31 and 38 apart, and forces the portion 31a and 38a intofrictional contact with theinnerperiphery of the outer drum I3. Theconstruction of the clutch mechanism is such that rotation 'of the'aircraft wheel, housing'4 and clutch mechanism V31, 38 relative to thedrum-member in one direction, i. e. forward rotation of the aircraftwheel, produces a considerable wedging or servo-action of thetorque-arms about the drum-member; whereas relative rotation of theclutch mechanism in theother direction produces onlyja proportion of`this torque, and no servo-action is obtained. Grease retainers 43 areprovided Yin the outer periphery of torque armsr 31 and 3B to lubricatethe frictional surface of the 'brake drum. K

The arxn 3 of theubifurcated bracket is considerably thicker than thearm 2 and is 'of rectangular shape. "On the face of the arm 3 remotefrom the flywheel a .substantially rectangular recess 44 (Figs. 2 and 4)is vprovided and from the base of vthe recess a hole, 'coaxial with thehousing, extends through the arm. .i A thrust rod 45 slidably extendsthrough said hole and has` one end projecting into the flywheel andtheother end projecting into said recess.l The end of the thrust rodprojecting into the ywheel abuts the disc 36, and torestrict frictionbetween the rotatable disc and the non-rotatable rod, said rod isprovided with Ya part-spherical,projection 46. The end of thevthr/ustrod is maintained in contact With the Ydisc bya helical spring 41encircling said rod which has one end abutting the arm 3 of the housingand the other end abutting an annular flange 48 extending vradially fromsaid rod adjacent the end Within the housing.

n g The end of the thrust rod remote from the nywheel projects a shortdistance out of the recess 44 in the face of the arm 3, and the portionof the thrust rod. within the recess is provided with a flat side.Pivotally secured to said side is one endof a cranked lever whichcomprises Va spindle 49 (Fig. 4), a lever arm 50 integral with one endthereof and a lever arm 5I secured to the other end thereof in a secondrecess 52 in the arm 3 parallel to the recess 44. The lever arms 50 and5l are diametrically opposed vand of equal length and the end of thelever `arm'5() is securedto the fiat of the thrust rod by a pin. i i

The arm 3 ofthe bifurcated. housing is provided with a second recess 52'adjacent the recess 44, the longitudinal axes of said-recesses beingparallel. The spindle of the cranked lever'is rotatably fit'- tedthrough a hole extending between said Arecesses 44 and 52. Thus thelever arm 50 -is situated in recess 44 'and lever arm 5I is situated inrecess 52. A sealing Washer 5,3 is provided in recess 52 to preventleakage 'of pressure uid through the hole between therecesses.

A rectangular valve body 54, Figure 3, selcured to the face of the arm 3remote 'from the housing, and saidybody converts the two recesses 44 and52 into ehan'bers. The chamber 52 is made substantially fluid tight bythe proiis'io'n of a sealing ring 54a around the periphery thereof.n Thevalve body is providedwith Va blind hole 55 (Fig. 2) communicating withtherecess 44 and Vaxially in lir'i'e lwith the thrust rod 45, into whichend of the thrust rod is slidably fltted; A fluid pressure conduit 56(Figs. -2 and `3) 'within the valve lbody eominunicates at one end withthe pressure chamber V52 fand at the other end with two brake operatingnozale's 51 (Fig. jl) adapted to be connected to two fluid pressureoperated mechanisms of the lassociated airoraft wheel brake.

:Avvalve lbeam 58 (Figsf3 and 4) is longitudinal'- n'r disposed withinthe pressure 'chamber 52, and .Y t;

gral rwith the end of Vthe lever arm 5l is loo in saidslot To the otherend of the talvebea'n is pivotally connectedone 'end of a tubular 'inletslide valve 60, which K4'operates in a liner 67| ii'tt'ed in a hole inthe valve body communicating ywith the pressure chamber r52, Vand has aportion adapted to abut the fwall 'of the chamber adj acent the housing.The slide Valve nis provided v4with a plurality of radially extendingholes 52 communicating with an annular groove in the outer periph'ery ofthe valve, and in'one position of said valve the recess communicateswith la plurality of lradially extending holes y63 through 'the liner(il.Y These holes communicate with an annular groove 54 around ntheperiphery of the hole the valve body and said groove in turncommunicates with a pressure conduit 6'41'1l (Figs. 1 and 3) leading toaninlet'noz'zle'fwhioh is adapted to be connected to "a source of 'fluidpressure. vA lter 3S is fittedvvithin the inlet nozzle to prevent entryof vforeign matter to the valve.

An exhaust valve plug 61 hasahead portion screw tted in a threaded holein the outer -face of the valve body 54 and a barrel portion slidablyhole extending through the body and communicating with the pressurechamber v52. The barrel portion is provided on k-its outer peripherywith an annular recess 68 of rectangular section and from the end of therecess remote from the pressure chamber a plurality of holes 59 extenddiametrically across lsaid portion. A hole 10 extends axially from thepressure charnber end of the barrel and terminates a short distance fromvthe holes 59 and an smaller coaxial hole 1| connects the end of hole 10and the june; tion of the diametric holes V69, The junction of the hole1I and the hole 1D forms the exhaust valve seat. a

An exhaust valve 12 is slidably fitted in the hole 10, one end thereofbeing tapered to seat on the exhaust valve seat and the other end beingpivotally connected to the Valve beam 58 'intermediate its ends andabout one-third of its `length from the slotted end. The vali/eisprovided with longitudinally extending nutes to enable pressure uid topass along the hole 10. A conduit (not illustrated) communicates at oneend with vthe annular recessj and at theoth'er end with an exhaustnozzle 13 (Fig. l). The valve beam`58 is provided with a leaf-spring 14which has one end secured to said beam adj acent 'the vinlet valve andthe other end abutting the wall of the pressure chamber adjacent thehousing and 'substantally in line vwith the exhaust valve. This 'springserves to ensure that ythe exhaust valve closes 7 before the inlet valveopens and opens after the inlet valve closes.

When the aircraft wheel is stationary, the flywheel housing, flywheeland drum-member associated therewith are likewise stationary, and theywheel is forced by the clockspring into such an angular positionrelative to the drum member that the flywheel beam is abutting thearcuate-shaped portions. In this position of the flywheel beam the twoballs 35 located in holes 3| in said beam are seated in the bottom ofthe V-shaped slot in the cam member and the thrustrod is urged by itsassociated spring into such a position that the valve beam maintains theexhaust valve in a closed position and the inlet valve in the openposition.

The apparatus operates as follows: As the Wheels of the landing aircraftsettle on the runway they commence to rotate, and as each wheel rotatesit causes the housing associated therewith to rotate. The stud extendingaxially from one wall of the housing and engaging in a hole in one ofthe torque arms of the clutch mechanism causes the said clutch to rotatewith the housing and with the drum-member stationary and the torque-armsrotating with the housing a considerable amount of torque is obtained,as` hereinabove described, which is sufficient to drive the drum almostinstantaneously. There is, in fact, a fractional amount of slip, justsufficient to cushion the shock and prevent damage to the ilywheel beamand associated parts. The beam of the flywheel is held against thearcuate-shaped stops of the drum member by the inertia of the flywheeland by the force of the clockspring, and hence there is no relativeangular movement between the flywheel and drum member. rThe cam member32 is keyed to the inner drum and so rotates with the drum and the twoballs 35 situated in the holes in the flywheel beam remain seated in thebottom of the V-shaped recess of cam 32 as shown in Fig. 2. No linearmovement is thus imparted to the thrust rod and the inlet Valve remainsopen and the exhaust valve shut. All the components within the housing,with the exception of the thrust rod, are now rotating at the same speedas the housing.

As the landing aircraft settles evenly on the runway the pilot applieshis control which allows pressure fluid to flow through the valve and tothe wheel brakes and so apply braking pressure. The wheel willdecelerate and the housing 4, rotated by the wheel, decelerates at thesame rate. The torque arms 37, 38 of the clutch mechanism aremechanically keyed to the housing l and also decelerate with the wheeland housing. A low torque value is obtained between torque arms anddrum-member during relative angular displacement in this direction andthis torque decelerates the drum comparatively slowly. If thedeceleration of the wheel is such that skidding is liable to occur, theflywheel 25, having a greater inertia, takes up an angular positionagainst the force of its associated clockspring such that the beam 30swings through the permitted arc between the arcuate segments, or stops,of the drum member 32. The can member is keyed to the drum Il, and hencethe balls 35 in the two holes in the flywheel beam 3Q ride up theinclined sides of the V-shaped recess in said cam member 32, forcing thedisc 3B, on the other side of the beam, in an axial direction away fromthe cam member.

The thrust-rod ll has one end abutting this disc, and is forced, againstits associated spring 41, away from the flywheel. This linear movement,'acting through the cranked lever 50 and through the valve beam 58 rstcloses the inlet valve 50 and then opens the exhaust valve 12. Thebraking pressure is thus relieved, and the wheel revolves normally oncemore before skidding actually occurs.

With the wheel and housing rotating normally the ywheel 25 urged by thespring 28 and due to the acceleration of the wheel, takes up itsoriginal angular position wherein the flywheel beam 33 is abutting oneside of the arcuate stops I8 of the drum member, as previouslydescribed, and in this position the balls 35 associated with theflywheel beam Sil, urged by the spring-loaded thrustrod 45 and disc 36,move back into the bottom of the groove in the cam member, and thispermits the thrust-rod to move suiliciently to first close the exhaustvalve 'l2 and then open the inlet valve 60, as previously described, andso re-apply the brakes.

This hunting will continue until the possibility of the tire skidding onthe surface of the runway is over. It must be appreciated that thishunting is extremely rapid and is imperceptible to anyone in theaircraft. For example, the housing may rotate at S500-4.000 revs. permin. and since less than half a revolution of relative angular movementbetween the flywheel and drum-member will suffice to open or close thevalve it will be seen that this operation will take but a fraction of asecond.

It frequently happens that aircraft bounce on landing, i. e. after theaircraft wheels have commenced to rotate and after the pilot has appliedthe brakes and unless the pilot manually removes the braking pressurebefore re-alighting, the unloaded wheels will lock and the aircraft willskid violently on re-allghting. This is obviously undesirable and in theapparatus of the present invention means are provided to prevent thisoccurring.

If the aircraft bounces on landing after the brakes have been applied,the weight of the aircraft is removed from the wheels, which lock, thatis to say, the wheel, housing and torque arms are renderednon-rotatable. As previously described, the greater inertia of theflywheel causes it to continue rotating against the slight frictionalresistance created between the torque arms and drum, and this angularmovement of the iiywheel relative to the drum compresses the clockspringand closes the inlet valve and opens the exhaust valve thereby relievingbraking pressure.

If the aircraft wheel were rolling normally over the ground theacceleration of the wheel would then angularly accelerate the drummember relative to the flywheel to open the inlet val-ve once more. Inthis case however the aircraft is airborne and the wheel is rotatingslowly or stationary. The flywheel beam 30 is abutting thearcuate-shaped segments l 8 of the drum member and the inertia of theflywheel is suilicient to carry the drum-member around with it, againstthe slight frictional resistance created between the stationary torquearms 31, 38 and the rotating. drum-member I7. The exhaust valve 12 ismaintained open and the inlet valve 6U closed until the frictionalresistance between torque arms and drum-member is suflcient to overcomeThe apparatus according to the invention may be used in braking anaircraft by twol distinct methods Bv the first methody the. pilotdesires to brake his aircraft in the shortest possible distance Withoutdamage to his tyres and landing gear. The maximum braking pressure iS.applied through the pilots Control as soon as the landing Wheels arerotating, and the automatioapparetus controls the pressure into thebrakes throughout the landing run- Thus the meen braking pressure isrestricted es the lending wheels are partly airborne and increases asthe load on the wheels` increases and reaches its maximum towards theend o f the landing run, when there is no danger of skidding. By thesecond method, the pilot has an unrestricted landing run and operateshis control to give only, say, one-third maximum pressure. Theautornaticl apparatus in this case will only restrict braking pressureat the early stages of the landing run, when the aircraft is partlyairborne, to prevent skidding. It is yof course to be understood thatshould an aircraft wheel encounter, e. g. a patch of oil or ice at anypoint ori the landing run, the automatic apparatus will immediately comeVinto operation to restrict braking pressure and so stop skidding.

' Apparatus in accordance with the invention is normally tted to'eachwheel of an aircraft which is tted with "brakes, so that the wheelsmaybe braked independently of one another. Any type of iluid pressureoperatd'brake may be tted Yto the wheel; preferably, however, the brakesare hydraulically operated.

What I claim is:

1. Apparatus for automatically controlling the braking pressure in anaircraftfluid pressure perated vwheel brake comprisinga'hou'sing"`rotatable by a wheel, a flywheel rotatable in and driven bysaid housing, a dru `meriber also rotatable in said housing and capableof limited angular displacementrelative to said ilywlcel;y meansmoveable axially by said angular displacement, and a valve mechanismadaptedto be connectedto a source of fluid pressurejto an exhaust and tosaid brake and operated by axial movement Qf said means, whereby onrelative angular displacement between the drum-member and flywheel inone direction the axially-moveable means operates the .valve mechanismto reduce the .brakinlg'pressure and on relative angular displacement inthe other direction the axially moveable means operates the valvemechanism to restore the braking pressure.

2. Apparatus for automatically controlling the braking pressure in anaircraft riluid pressure operated Wheel brake comprising a housingrotatable by a wheel, a ywheel rotatable in and driven by said housing,a drum-member also rotatable in said housing and capable of limitedangular displacement relative to said flywheel on a change of relativeangular velocity, a clutch mechanism rotatable by the housing anddriving the drum-member, a spring associated at one end with saidflywheel and at the other end with said drum-member and urging saidflywheel into a predetermined angular position relative to saiddrum-member, means movablye axially on relative angular displacement ofsaid flywheel from said predetermined position and a valve mechanismadapted to be exhaust and to said brake and operated by axial connectedto a source of fluid pressure, to an gular displacement between the drummember movement of said means, whereby on relative anand ilywheel in onedirection the axially-movfv able means operates the valve mechanism toreduce thev braking pressure and on relative ane gular displacement inthe other direction the axially movable means operates the valvemechanism to restore the braking pressure.

3. Apparatus for automatically controlling the braking pressure in anaircraft fluid pressure operated wheel brake comprising a housingrotatable with a wheel, an annular flywheel rotatable in and driven bysaid housing having a.v

beam extending diametrically across then interior thereof, a drum-memberalso rotatable in said housing and within the inner periphery of saidflywheel and provided with two diametrical `ly opposed stops adapted tocontact the flywheel beam and restrict angular displacement of theywheel relative to the drum-member, a clutch mechanism rotatable by thehousing and driv-A ing the drum-memberl a coil spring associated at oneend with said ilywheel and at the other c nd with said drum-member andurging said flywheel into a predetermined angular positionl sure and onrelative angular displacement in the other direction the axially movablemeans op: erates the valve mechanism to restore the braking pressure`f1. Apparatus according to claim 3 wherein the drum-member comprisesinner and outer coaxial drums and the clutch mechanism comprises twopart-annular torque arms located between said drums and spring-urgedapart at oneyend,

each of said torque arms having a part at one extremity thereoffrictionally engaging with the inner wall of the outer drum.

5. Apparatus according to claim Svcomprising a cylindrical cam memberfitting in the inner periphery of the drum-member and rotatable withsaid drum-member by dogs engaging in' axially extending grooves in theinner peripheryof said drum member, a V-sectioned recess in one face ofsaid cam member, two balls located in adjacent holes equispaced lone oneach side of the centre of said .flywheel beam and seated in the bottommined position of the flywheel relative to the drum-member, a discslidably iltting in the inner periphery of the drum-member on the otherside of the beam and a thrust-rod having one end spring urged intocontact with said disc, whereby on relative angular movement between theflywheel and drum-member the balls ride up the inclined sides of saidV-sectioned recess and force the disc and the thrust-rod in an axialdirection against their associated spring.

6. Apparatus according to claim 5 wherein said valve mechanism comprisesa pressure chamber having a conduit adapted to communicate with a uidpressure operated brake, an inlet conduit adapted to communicate with asource of fluid pressure and an an angularly moveable valve beam locatedin said chamber having one end mechanically connected to one end of saidaxially moveable means, an inof said recess in said predeter" let valvein said inlet conduit and an exhaust valve in said exhaust conduit, saidvalves being linked to said valve beam, whereby movement of said axiallymoveable means in one direction operates the valve beam to close theinlet valve and open the exhaust valve, and movement of said axiallymoveable means in the other direction similarly opens the inlet valveand closes the exhaust valve.

'7. Apparatus according to claim 6 wherein relative angular displacementbetween the ilywheel and drum-member in one direction acting through thecam-member and balls moves the thrust-rod axially against its associatedspring to operate the valve beam and close the inlet valve and open theexhaust valve, and relative angular displacement of the flywheel anddrum-member in the other direction similarly opens the inlet valve andcloses the exhaust valve.

8. Apparatus according to ,claim 7 wherein the valve beam is springurged in one direction whereby the exhaust valve closes before the inletvalve opens and opens after the inlet valve closes.

9. Apparatus according to claim 4 wherein one of the torque arms isprovided with a wedgeshaped portion which fits into a rectangular recessformed in the adjacent end of the other torque arm to produce anincreased torque when said arms are spring-urged apart to contact theinner wall of said outer drum.

10. Apparatus for automatically controlling the braking pressure in anaircraft fluid pressure operated wheel brake comprising a housingrotatable by a wheel, a flywheel rotatable in said housing, a drummember also rotatable in said housing and capable of limited angulardisplacement relative to said iiywheel, a rubber tire tted to an outerperiphery of said housing to provide drive means for said housing, andadapted to contact a rotatable part of the wheel, a thrust rod movableaxially by said angular displacement and a valve mechanism adapted to beconnected to a source of fluid pressure, tov exhaust, and to said brake,and operated by axial movement of said thrust rod, whereby on relativeangular displacement between the drum member and the flywheel in onedirection the thrust rod operates the valve mechanism to reduce thebraking pressure and on relative angular displacement in the otherdirection the thrust rod operates the valve mechanism to restore thebraking pressure.

11. Apparatus for automatically controlling the braking pressure iniluid operated wheel brakes which comprises a housing rotatable byengagement with a wheel, a drum rotatable coaxiallyl within said housingrelatively to said housing, an

over riding clutch connection from said housingV to said drum and havinga wedging engagement in forward direction and a slipping drag in overriding movement, a cam rotating with said drum, a flywheel driven bysaid drum and having a limited forward movement relative to said drum, acam follower carried ,by said ilywheel and displaced by said cam onrelative displacement of said ywheel and drum and a valve for brakefluid having an inlet port, an outlet port, and an exhaust port, andactuated to close said inlet port and open said outlet port insuccession on displacement of said cam follower by said cam.

12. The apparatus of claim 11 having a spring urging said flywheel intoa predetermined position relative to said drum.

13. The apparatus of claim 11 in which salu ywheel encircles said drumand has a diametrical bar carrying said cam follower and said drum has apart transverse to said diametrical bar positioned to engage said bar todrive said flywheel forwardly.

14. The apparatus of claim 11 in which said over riding clutch comprisesan arcuate arm pivoted on one element of the drum and housing assemblyand a spring pressing the free end of this arm against the other elementof said assembly.

15. The apparatus of claim l1 in which said valve is actuated from saidcam follower by a lever, and a spring pivot for said lever reactingadjacent the point of attachment to the exhaust valve to close saidvalve prior to opening of the inlet valve.

16. The apparatus of claim 11 in which said over-riding clutch comprisesa pair of arcuate arms located within the drum, one of said arms beingpivoted at one end on the housing and engaging at the other end with oneend of the other arm, and a spring located between the opposite ends ofsaid arms to press said ends apart.

HENRY W'ILLIAM TREVASKIS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,107,823 Hallet Feb. 8, 1938 2,163,731 Hallet June 27, 19392,225,978 Carmichael Dec. 24, 1940 FOREIGN PATENTS Number Country Date48,806 France May 3, 1938

